1. Field of the Invention
This invention relates to cutting glass sheets and in particular to a cutting head assembly that responds quickly to changes in the load applied to a cutting wheel of a cutting assembly to control the quality of the cut glass edge.
2. 2A Technical Considerations
The quality of a cut glass edge obtained in a cutting operation using conventional scoring and breaking techniques depends in part upon the quality of the scored line. It is preferred to have a constant scoring depth which provides a uniform edge quality after removing trim from the glass sheet. When scoring a curvilinear line, and in particular when scoring sharp corners of a glass sheet, for example an automotive window, the speed at which the scoring wheel travels along the glass sheet is reduced so that the wheel can better follow the desired contour to be scored. As scoring speed decreases, the load applied to the cutting wheel must be increased to maintain the desired scoring depth. The pressure on the cutting wheel can be provided by a pneumatic cylinder and controlled by varying the load from the cylinder. However, these types of cylinders have a slow response time and cannot increase and decrease the load applied to the cutting wheel at a fast enough rate to optimize cutting speed. As a result, when scoring the glass at optimal speed, portions of the scored perimeter will not be scored at the optimal load required to provide constant scoring depth.
It would be advantageous if variations in the loading required to maintain the proper scoring depth could be controlled to precisely provide the necessary loading required for a given scoring speed and further to be able to quickly change the load in response to changes in scoring speed so as to maintain optimal scoring depth and consistent edge quality while providing maximum scoring speed.
2B. Patents of Interest
U.S. Pat. No. 3,742,793 to Gray et al. teaches a cutter assembly and a double acting pneumatic cylinder and piston. The cutter assembly is connected to the piston which is operable to urge the cutter assembly towards the surface to be scored.
U.S. Pat. Nos. 3,756,104 to Bier et al. and 3,760,997 to Bier teach the cutting of glass using a cutter head connected to a constant reluctance motor. Pressure exerted by the cutter head responds to changes in the current supplied to the motor making it possible to vary the depth of the score as desired during the making of the pattern cut.
U.S. Pat. No. 3,880,028 to Frederick Jr. teaches a method and apparatus for monitoring and controlling glass cutting. Sound waves produced by scoring the glass in a cutting operation are detected and correlated to the quality of the cut. Scoring speed and pressure on the scoring tool are controlled in response to the detected sound level.
U.S. Pat. Nos. 4,137,803 and 4,204,445 to Goldinger teach a scoring device that will maintain a constant cutting force on a glass sheet despite irregularities in glass thickness or oscillation of the scoring head carriage assembly.
U.S. Pat. No. 4,171,657 to Halberschmidt et al. teaches a numerically controlled cutting machine. The cutting head is connected to a pressure control tube which in turn is connected to a hydraulic control device which changes the cutting pressure during the scoring operation.